Method and device for producing three-dimensional models

ABSTRACT

The present invention relates to a method for producing three-dimensional objects based on computer data by repeated application in layers of a medium containing particulate material and selective solidification of the medium, whereby a feedstock made of medium in a build space is provided and a layer application of the medium takes place on a surface of the feedstock bordering the build space at an angle β and a solidification according to computer data occurs by use of a solidification unit, characterized in that the feedstock is not moved during build-up of the object.

The invention relates to a method for manufacturing three-dimensional models as expressed in the generic concept of patent claim 1 as well as a device as expressed in the generic concept of patent claim 8.

A method for producing three-dimensional objects from computer data is described in the European patent specification EP 0 431 924 B1. In this method, a particulate material is deposited in a thin layer onto a platform, and a binder material is selectively printed on the particulate material, using a print head. The particle area onto which the binder is printed sticks together and solidifies under the influence of the binder and, if necessary, an additional hardener. The platform is then lowered by a distance of one layer thickness into a build cylinder and provided with a new layer of particulate material, which is also printed as described above. These steps are repeated until a certain, desired height of the object is achieved. A three-dimensional object is thereby produced from the printed and solidified areas.

After it is completed, this object produced from solidified particulate material is embedded in loose particulate material and is subsequently removed therefrom. This is done, for example, using an extractor. This leaves the desired objects, from which the remaining powder is removed, for example by brushing.

Other particulate material-supported rapid prototyping processes work in a similar manner, for example, selective laser sintering or electron beam sintering, in which a loose particulate material is also deposited in layers and selectively solidified with the aid of a controlled physical radiation source.

All these methods are referred to collectively below as “three-dimensional printing methods” or “3D printing methods”.

A common feature of all the above-mentioned embodiments is that the manufacturing process in build containers limits the size and weight of the desired products, this especially being due to the build container.

A method enabling the production of moldings of greater lengths is described in the German patent application DE 10 2010 015 451 A1. Proposed for this purpose is to deposit a feedstock of particulate material on a conveyor belt and to build three-dimensional components in layers upon it. The components can therefore be constructed continuously and, for example, unpacked by the conveyor belt after exiting from the device. With this method, however, the component length is limited by the length of the device used.

The object of the present invention is to provide a 3D printing method and device and a method enabling the manufacture of very long and heavy components and mitigate the disadvantages of the prior art or even avoid them entirely.

This object is achieved by a method according to patent claim 1 and a device according to patent claim 8.

According to the present invention, a method for producing three-dimensional objects based on computer data is provided by repeated application in layers of a medium containing particulate material and selective solidification of the medium, whereby a feedstock on a build space is provided and a layer application of the medium by means of a coating unit takes place at an angle β upon the bordering surface of the feedstock and a solidification according to computer data occurs by use of a solidification unit and whereby the feedstock is not moved during build-up of the objects.

It is now proposed to continuously build upon a stationary feedstock whereby, if necessary, the device parts used for application and, if necessary, selective solidification, are moved in relation to the feedstock.

Preferably, the coating unit and/or solidification unit have an angle of α<90° to the build plane of the build space and are moved in relation to the feedstock.

According to one especially preferred embodiment of the present invention, the angle α is smaller than the angle β.

Furthermore, it is also possible that the angle α is larger than the angle β.

With one method according to the present invention, it is now possible that the manufactured objects can be unpacked from the particulate material without interrupting the build process of the feedstock and execution of solidification. For example, the unpacking could occur continuously.

The term feedstock, likewise called aggregate material, is generally understood to be a mixture of solid particles (for example granulates) that is loosely mixed.

The principle force acting between the particles of a feedstock is friction as well as adhesion. In the case of non-round particles there is also the factor of self-blocking, and in the case of rough particles micro-grouting, even electrostatic forces under certain circumstances.

Due to the influence of gravity, an equilibrium of shearing stresses at the contact surfaces is set up in the aggregate material by which the feedstock achieves its stable shape.

The particles can have various particle sizes and compositions. For example, they may be composed of pure substances or composed of mixtures connected solidly to each other.

If aggregate materials are set in motion, they behave like fluids and can be described in terms of fluid dynamic formulas.

The angle β can therefore also be called the “pouring angle”.

According to the present invention, a coater is provided at the formation of the pouring cone surface, which can be either flat or curved, for instance at the front side of the feedstock, and this coater applies new particle material to the feedstock.

Preferably, it may be provided that the coater moves over the feedstock at an angle α to the build surface that is preferentially exactly horizontally oriented, said angle smaller than the pouring angle β of the particle material. According to one preferred embodiment of the invention, it is ensured that the layer of newly deposited particulate material remains at the desired area and does not slip off.

Moreover, it may prove advantageous if additional limitation walls are established during build-up of the objects. One such embodiment has the advantage that by means of it the feedstock can be limited, if needed, by means of the limitation walls created by the solidification unit.

Depending on the embodiment of the present method, it may prove advantageous that the coating unit and/or solidification unit essentially moves horizontally. In addition, it may likewise be advantageous that the coating unit and/or solidification unit essentially moves in an involute manner.

Preferably, the coating unit and/or solidification unit moves on a coordinate system placed at an angle α to the build plane of the build space and parallel to the build plane of the build space.

According to an especially preferred embodiment of the present invention, supplemental structures are formed that hinder a slipping down of the medium in the material cone.

A device according to the present invention producing three-dimensional objects based on computer data by repeated application in layers of a medium containing particulate material and selective solidification of the medium, having a feedstock made of the medium in a build space and a coating unit for layer application of the medium at an angle β upon the bordering surface of the feedstock and additionally having a solidification unit for solidifying the medium according to computer data. However, the feedstock does not move during build-up of the object.

Preferably, in a device according to the invention, the coating unit and/or solidification unit has an angle of α<90° to the horizontal plane of the build space and is capable of moving relative to the feedstock. Depending on the embodiment, the angle α can thereby be smaller, greater or equal to the angle β.

In a device according to the invention, the solidification unit can have a droplet generator. Furthermore it may also possible that it has a radiation source.

The coating unit and/or solidification unit may preferably be movable on a coordinate system placed at an angle α to a build plane of the build space and movable parallel to the build plane of the build space.

According to one preferred embodiment, the build space is a floor, preferably a work bay floor of a production facility. It is furthermore possible that the build space has a building platform and/or slidable floors and/or an intermittent conveyor belt along the linear guide.

It may also be preferable that the unit including the coating unit and solidification unit is horizontally moved on tracks.

Moreover, it may prove advantageous that the unit rests on walls that it builds as it proceeds.

The angle α can advantageously be adjusted on the device in order to harmonize the device to the particulate material. In addition, on this side a device is mounted that selectively solidifies the particulate material alongside the particulate material plane defined by the coating unit. This solidification unit can be a print head which releases small fluid droplets on the particulate material with the result that the particulate material solidifies there in a locally demarcated manner. Other devices can alternatively be employed, such as a radiation source for high energy beams.

After completion of a layer comprised of a coating and subsequent solidification, the device is transported in the direction of the forming feedstock a distance amounting to the layer thickness. Depending on the size, the device can be conveyed e.g. on a rail system. Slippage-free drives (for example) rack-and-pinion systems must ensure precision of the movement.

The feedstock can be constructed directly on the floor upon which the device is operated. This can also be the work bay floor of a production facility. However, manufacture may also take place outdoors if the size of the device and the desired components require such. The device can likewise function on interchangeable platforms.

A substantial advantage of the method and the device is the simplicity of the technical execution. In comparison to the prior art, build containers for reception of the feedstock are dispensed with. The feedstock is also not moved relative to any wall, which reduces wear as well as the driving force and drive performance and mitigates tendencies to malfunctions in the feedstock. The feedstock is constructed on a support surface. The support surface may be a surface of a floor, a surface of a platform, or a surface of a conveyor belt.

To prevent slipping down of the feedstock, a grid structure can be printed along with it. This stabilizes the particulate material feedstock and also helps to hinder the uncontrolled discharge of the particulate material in the break-out zone later on.

The length of the feedstock from the printing unit right up to the break-out zone depends on the respective solidification process. This can be determined, for example, by simply measuring. The length can be designed in a way that the feedstock remains a certain retention period in the contiguous situation to e.g. give the liquid time to react with the particulate material in order to develop adequate stability. It is also possible that the retention period can be used to cool down the feedstock in a controlled fashion from the side opposite the solidification zone. There are also conceivable cases where both effects are jointly used. In both cases, a gradient results that conforms to the layer-building and passes through the feedstock.

In contrast to methods in build containers, in this case the layers reach the break-out zone in the same sequence as they were built. The retention period can thus be held nearly constant in the particulate material feedstock for all areas. This is a great advantage since in this way the curing can proceed in a much more controlled manner and is thereby accompanied by less delay.

The break-out zone described herein and of the device is more accessible in comparison to conventional methods. If the feedstock is constructed on a work bay floor, then every mold can be easily retrieved by means of tools, forklifts or a hall crane. A large device length makes it possible to nearly arbitrarily select the time point at which to unpack.

Since the components can be laid stacked over one another in the direction of gravity, it may be required to embed the components with support structures that also have to be built and that are able to develop sufficient backing effect even in the absence of surrounding particulate material and to hold the components in position until they are removed.

If the particulate material is reusable in the process, then it can be collected in the break-out zone and again fed into the application process after a possible pass through a preparation section. In the preparation section, it may, for example, be necessary to perform a sifting of the particulate material and/or a regulated feed-in of fresh particulate material.

In the case of horizontal orientation of the conveyance plane, the solidification period, respectively, the break-out period only affects the length of the device.

Such a system enables the processing of a multitude of different materials. Possible materials also include sand, gypsum, metal particulate material or other inorganic particulate materials as well as plastic particulate material, flour and other organic particulate materials.

The system and the process permit a wide spectrum of varied applications, such as the manufacture of molds and models for metal casting as well as the production of components of the most diverse types. Likewise, an interesting advantage is that the continuous procedure also allows production of longer components without having to modify the device.

For the purpose of more detailed explanation, the invention is described in further detail below on the basis of preferred embodiments with reference to the drawings.

In the drawing:

FIG. 1 An isometric view of a device according to the prior art;

FIG. 2 A sectional view of a device according to the prior art;

FIG. 3 An illustration of the feedstock for definition of the machine angle;

FIG. 4 A sectional view of a preferred embodiment of the invention;

FIG. 5 A side view of one particularly preferred embodiment of the invention;

FIG. 6 An illustration of a feedstock produced according to the invention;

FIG. 7 A sectional view of one preferred embodiment of the invention;

FIG. 8a A side view of another preferred embodiment of the invention, with a rotating build platform and conical powder cake;

FIG. 8b A view of the embodiment of FIG. 8a from above;

FIG. 9 A sectional view of a further preferred embodiment of the invention;

FIG. 10 A representation of one preferred embodiment of the invention with build platforms;

FIG. 11 A representation of one preferred embodiment of the invention with material silo; and

FIG. 12a-d The various process steps of a preferred embodiment of the invention.

FIG. 1 shows a device according to the prior art. A coating unit (2) applies a layer consisting of particulate material on a build platform (3). At the conclusion, with the aid of computer-provided data, the particulate material is selectively solidified. In FIG. 1, this area is indicated by (4). The perpendicular is indicated here by the reference symbol (5). After solidification the build platform (3) is lowered by one layer thickness and then another layer is created.

In FIG. 2 the same device is depicted in sectional view. Several layers have already been created. A limiting factor during the method according to the prior art is the build container depicted in the Figure as (7). After a certain build height (6) the container (7) must be emptied or exchanged.

FIG. 3 illustrates a particulate material feedstock that can be made without limitations. This has a front-side plane that includes a certain angle (8) to a horizontal plane (10). The feedstock consists of individual layers (9) and can be produced as shown in patent DE 10 2010 015 451 A1. The angle (8) shown here is hereinafter called the machine angle.

FIG. 4 depicts one preferred embodiment of the invention. The Figure shows a sectional view comparable with FIG. 2. According to patent claim 1, the particulate material feedstock here is not moved relative to the machine, but rather it remains motionless. A coordinate system in the hall where the device is located is hereby fixed. On the other hand, the device moves.

After some time of system operation, the scenario represented in FIG. 4 results. With increasing build time, the material feedstock (12) becomes ever longer whereby the carrier unit (11) moves with solidification unit (1) and coating unit (2) in the build direction (15) over a horizontal plane (14). The mold parts (4) to be produced lie stationary in the feedstock.

FIG. 5) shows a technical arrangement of the device. The carrier unit is hereby implemented as vehicle (25). This is guided over a rail track (13). The rail track (13) is designed according to the required degree of precision and measurement system used for position detection. Linear guidance systems can be used here for the highest degree of guidance precision and rigidity. Tracks resembling railroad tracks can be used if a high degree of precision is not required. It is also conceivable to simply use wheels to roll on plane (14), however this is connected with a corresponding amount of measurement effort.

Various mechanisms can be used as drive systems. A very high degree of motion precision and thus of the layer thickness can be achieved with combined linear units that contain a ball screw drive. Rack-and-pinion systems and preloaded cog wheels can also achieve small position deviations. Frictional drives can also be used. However, the position measurement and control must be adapted to this type of drive.

FIG. 6 shows a feedstock made of particulate material. Such a feedstock would be produced by a coating unit that has a horizontal slot from which the particulate material can run out. The natural angle of repose of the material results in the basic geometrical shape of a truncated pyramid. The device must be implemented correspondingly large enough to prevent penetration of the material into the rail system. As illustrated in FIG. 6, the angle between the horizontal direction 80 and the direction of incline 82 of a bordering surface 86 may be the pour angle 84 of the material. Supplemental structures 88 may be formed that hinder a slipping down of the material.

This situation can be improved with a device according to patent claim 4. In this case, the solidification unit (1) creates walls that laterally limit the feedstock. In this way, a parallelepiped is created with a significantly lower area requirement.

Depending on the type of solidification mechanism used, the unpacking of mold parts (4) can proceed after a certain amount of time after the layers are created. The solidification time and the safety distance are the determining factors for the unpacking length. The safety distance is necessary so that unpacking does not disturb the building process.

If the material feedstock (12) is constructed directly on the work bay floor (14), then it can be unpacked in an especially simple manner. For this purpose, any tools can be used, such as forklifts or cranes. The rail system (13) according to the invention must then be implemented appropriately sturdy.

A further embodiment of the invention is depicted in FIG. 7. A stationary feedstock on a horizontal plane is also used in this case. The angle between the carrier unit (11) and the horizontal plane amounts to 0 degrees here. In contrast to patent DE 10 2006 030 350 A1, the vertical movement does not take place by means of an axis system, but rather using a progression of carrier unit (11) toward the already built walls of the feedstock. The walls exhibit a special geometry that ensures precise positioning.

FIG. 8 and FIG. 9 depict a further embodiment of the invention according to patent claim 1. In this case and deviating from the above-mentioned embodiments, the feedstock is produced in a rotary manner and not in a linear fashion. For this purpose, the carrier unit is guided in an involute motion around machine axis (20). Compared to the above-mentioned descriptions, the coating unit is turned 90° and can be continuously operated. The solidification unit can also be continuously operated. A build cone (21) can be used to start the system. This device type requires the data for the molds (4) to be skewed not only linearly, but also according to polar coordinates.

Instead of building the material feedstock on the work bay floor, a build platform (22) can also be used. This can also use the rail system of device (13) as depicted in FIG. 10. After the building process, the platforms can be exchanged if needed.

The materials needed for the building process can be supplied to the device via flexible hoses. These materials could include e.g. particulate material, binder or electrical energy. If critical materials are used or the circumstances on-site do not allow such, then the materials can also be moved with the carrier unit. By way of example, FIG. 11 shows an accompanying particulate material silo (24) conveyed on the machine rail system.

FIG. 12a-d show a preferred embodiment of the invention in which the material feedstock (12) is built on a conveyor belt (28). The conveyor belt (28) extends over the build space (6) and an unpacking area (27).

In the building process, a process plane (29) that carries the layer-generating tools (1) and (2) moves layer by layer within build space (6) by means of linear units (26).

The conveyor belt (28) remains motionless until the first build space (6) is entirely built upon.

The completed component is subsequently transported into the unpacking area (27) with the conveyor belt. At the same time, the process plane (29) moves into its initial position. If the process plane (29) and the material feedstock (12) are positioned, then the building process is immediately continued on the material feedstock (12). The completed components can be removed in unpacking area (27). While doing so, the building process does not need to stop.

LIST OF REFERENCE NUMERALS

-   1 Solidification unit -   2 Coating unit -   3 Build platform -   4 Component (part of which is being built) -   5 Gravitational direction -   6 Build space -   7 Build container -   8 Machine angle -   9 Layers -   10 Horizontal reference plane -   11 Unit with coating unit and solidification unit -   12 Stationary feedstock -   13 Rail system -   14 Work bay floor -   15 Direction of construction -   16 Pouring feedstock -   17 Flat area created by the coating unit -   18 Wall created by solidification unit -   19 Irregularly leveled area -   20 Rotation axis of the device -   21 Ancillary cone for starting the system -   22 Build platform -   23 Feedstock on the build platform -   24 Material silo -   25 Carrier vehicle -   26 Linear drive -   27 Unpacking area -   28 Conveyor belt -   29 Process plane 

What is claimed is:
 1. A device for producing three-dimensional objects based on computer data by repeated application in layers of a medium containing a particulate material and selective solidification of the medium, wherein the layers include sequential layers, wherein the device comprises: a support surface for supporting a feedstock made of the medium during the production of a build object; a build space over the support surface; a coating unit for depositing the particulate material on a build surface of the feedstock; and a solidification unit for solidifying the medium according to computer data; wherein the build surface has a build angle, α, relative to the support surface, wherein α is greater than 0 degrees; wherein the feedstock has bordering surfaces adjacent to the build surface, each bordering surface having an angle β relative to a horizontal plane; and wherein the coating unit and the solidification units move in a direction parallel to the support surface away from the feedstock between application of the sequential layers so that the feedstock is stationary during build-up of the build object until the build object is complete or until the build space is entirely built upon.
 2. The device of claim 1, wherein the solidification unit has a droplet generator.
 3. The device of claim 2, wherein the coating unit and the solidification unit move on a coordinate system placed at the angle α relative to the support surface and parallel to the build surface of the feedstock.
 4. The device of claim 3, wherein the angle α is less than 90 degrees and the support surface is a horizontal surface.
 5. The device of claim 4, wherein i) the support surface is a work bay floor of a production facility, ii) the support surface is a surface of a build platform, iii) the support surface includes slidable floors, iv) the support surface is a surface of an intermittent conveyor belt that moves along linear guides after the build object is complete or after the build space is entirely built upon, v) or any combination of (i) through (iv); and wherein the coating unit and solidification unit are horizontally moved on tracks.
 6. The device of claim 4, wherein the support surface has an intermittent conveyor belt that moves along linear guides after the build object is complete or after the build space is entirely built upon.
 7. The device of claim 6, wherein the coating unit and solidification unit are horizontally moved on tracks.
 8. The device of claim 7, wherein the device includes a carrier unit that moves with the solidification unit and the coating unit in a build direction.
 9. The device of claim 8, wherein the device includes rail tracks for guiding the carrier unit.
 10. The device of claim 8, wherein the device includes a drive system having a ball screw drive.
 11. The device of claim 8, wherein an angle between the carrier unit and a horizontal plane is zero degrees.
 12. The device of claim 11, wherein the device includes a conveyor belt extending over the build space and over an unpacking area.
 13. The device of claim 8, wherein the tracks are horizontal.
 14. The device of claim 1, wherein the solidification unit rests on walls that the solidification unit builds as the solidification unit proceeds.
 15. The device of claim 1, wherein the coating unit and/or solidification unit are/is angled at the angle α, wherein the angle α is less than 90 degrees, relative to the support surface and are/is moved in relation to the feedstock.
 16. The device of claim 15, wherein i) the support surface is a work bay floor of a production facility, ii) the support surface is a surface of a build platform, iii) the support surface includes slidable floors, iv) the support surface is a surface of an intermittent conveyor belt that moves along linear guides after the build object is complete or after the build space is entirely built upon, v) or any combination of (i) through (iv); and wherein the coating unit and solidification unit are horizontally moved on tracks.
 17. The device of claim 1, wherein the solidification unit has a radiation source.
 18. The device of claim 17, wherein the coating unit and the solidification unit move on a coordinate system placed at the angle α relative to the support surface and parallel to the build surface of the feedstock.
 19. The device of claim 1, wherein the device includes a material silo that moves on tracks.
 20. The device of claim 1, wherein the solidification unit and the coating unit move in a circular direction.
 21. The device of claim 1, wherein the support surface is a surface of a build platform, the build platform moves along a first set of tracks and the device includes a carrier unit that moves along a second set of tracks in the same direction, wherein the carrier unit supports the coating unit and the solidification unit.
 22. The device of claim 1, wherein the device includes a conveyor belt that moves in a first direction and a linear drive for moving the solidification unit and the coating unit in a direction parallel to the first direction, wherein the movement of the solidification unit and the movement of the conveyor belt in the first direction are independently controlled.
 23. The device of claim 1, wherein the angle β is an acute angle.
 24. The device of claim 23, wherein the angle β is the angle of repose of the particulate material. 